Question

Here is my code:

#include <gtk/gtk.h>

static int counter = 0;
static PangoLayout* layout;
static GdkGC* gc1;
static GdkGC* gc2;
//**/static GMutex* mu;

static gboolean on_expose_event(GtkWidget* widget, GdkEventExpose* event)
{
    gchar the_string[20];

    //**/g_mutex_lock(mu);
    gdk_draw_rectangle(GDK_DRAWABLE(widget->window), gc1, TRUE, 0, 0, widget->allocation.width, widget->allocation.height);
    snprintf(the_string, 20, "%d", counter);
    pango_layout_set_text(layout, the_string, -1);
    gdk_draw_layout(GDK_DRAWABLE(widget->window), gc2, 180, 120, layout);
    //**/g_mutex_unlock(mu);

    g_print (".");
    return FALSE;
}

gpointer func(gpointer data)
{
    //**/g_usleep(10000);
    GdkWindow* window = GDK_WINDOW(data);
    while(TRUE)
    {
        gdk_window_invalidate_rect(window, NULL, FALSE);
        //**/gdk_window_process_updates(window, FALSE);
        if(counter % 100 == 0) g_print("X");
        g_usleep(10);
        ++counter;
    }
    return FALSE;
}

int main(int argc, char** argv)
{
    GtkWidget* window;
    GtkWidget* drawer;
    GdkColormap* colormap;
    GdkColor color;

    g_thread_init(NULL);
    gdk_threads_init();
    gtk_init(&argc, &argv);

    //:Create widgets and 
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    drawer = gtk_drawing_area_new();
    gtk_widget_set_size_request(drawer, 400, 300);
    gtk_container_add(GTK_CONTAINER(window), drawer);
    //.

    gtk_widget_show_all(window);

    //:Initializing Graphic Contexts
    colormap = gtk_widget_get_colormap(GTK_WIDGET(drawer));
    layout = gtk_widget_create_pango_layout(GTK_WIDGET(drawer), NULL);
    gc1 = gdk_gc_new(GDK_DRAWABLE(GTK_WIDGET(drawer)->window));
    gc2 = gdk_gc_new(GDK_DRAWABLE(GTK_WIDGET(drawer)->window));
    gdk_color_parse("#000", &color);
    gdk_colormap_alloc_color(colormap, &color, FALSE, TRUE);
    gdk_gc_set_background(gc1, &color);
    gdk_color_parse("#fff", &color);
    gdk_colormap_alloc_color(colormap, &color, FALSE, TRUE);
    gdk_gc_set_foreground(gc2, &color);
    //.

    g_signal_connect(G_OBJECT(window), "destroy", G_CALLBACK(gtk_main_quit), NULL);
    g_signal_connect(G_OBJECT(drawer), "expose_event", G_CALLBACK(on_expose_event), NULL);

    //**/mu = g_mutex_new();
    //Run the problematic thread!
    g_thread_create(func, GTK_WIDGET(drawer)->window, TRUE, NULL);

    gdk_threads_enter();
    gtk_main();
    gdk_threads_leave();

    //**/g_mutex_free(mu);
    return 0;
}

It’s a multithreaded program, and did nothing so especial! It just force a GtkDrawingArea to redraw itself from the main thread (GTK+ main loop).

My problem (or GTK+ problem!) is that after a long time running (maybe 0.5, 1 or 4 minutes!), the expose event will not work (does not response to my requests until I’m resizing the whole window!)! Please, compile and run the code to check this situation. I added some print commands which may help! but i can’t detect the problem, because of my little experience.

I hoped this program can redraws its context for almost always, but it didn’t (or couldn’t). What can i do to solve this problem? Maybe i should report a bug to GTK+ developers?

I’m using Debian + GCC + GTK2.20

Answer 1

Most likely, you need to surround your gdk_window_invalidate_rect() call with gdk_threads_enter()/gdk_threads_leave() pair. Read the gdk threads for more information about gtk and threads. Look at the example there.